Investigation into the Effect of the Duration of Exposure on the Behaviour of GPC at Elevated Temperatures

Abstract

Ordinary Portland Cement (OPC) Concrete has long been used in the construction industry as a primary material owing to its versatility, superior performance, low cost, easy workability and availability of accepted standards of practice. The readily available raw materials for the manufacture of cement, and subsequently for concrete itself, have been a driving force for the acceptance of concrete as a construction material worldwide. Recently however, OPC concrete has come under scrutiny over its large carbon footprint. This is largely due to the energy intensive manufacturing process of cement and the extensive use of virgin material in cement production. Focus is therefore shifting to engineer new construction materials that offer similar advantages to that of OPC concrete while being environmentally friendly. Geopolymer Concrete (GPC) is such a material. It has emerged during the last decades, and has been found to possess excellent engineering properties as well as enormous benefits on the sustainability front. The current study is conducted to investigate the compressive strength of GPC up to temperatures of 1000 o C for varying duration of exposure time. It was found that when tested at temperatures of 600 o C, 800 o C and 1000 o C, the GPC samples exhibited a higher compressive strength (8-18%). However, the samples tested after cooling recorded a residual compressive strength 25-50% lower than the ambient strength. Yet, the residual strength of GPC is significantly higher than that of OPC. The duration of exposure time was found to have an insignificant effect on the strength properties of GPC, especially at higher temperatures. Scanning Electron Microscopy (SEM) was used to reveal the changes to the micro-structure that took place after exposure to high temperatures and to get a useful insight into the behaviour of geopolymers.